AUDITORY SENSITIVITY OF THE WHITE RAT 323 



whistle pitch as to the standard in spite of the fact that only- 

 failure attended the use of the tuning fork. 



Control 10. — The difference in the results obtained in controls 

 8 and 9 may have been due to differences in the complexities 

 of the stimuli. This is true although long tests were made 

 (as described above) in a fruitless endeavour to set up a dis- 

 criminative reaction to a common chord, 512 d.v. plus 640 d.v. 

 In the present control the chord 1152 d.v. plus 1280 d.v. was 

 sounded on forks in place of using the standard whistle. The 

 animals again failed in their reactions. If, in spite of the fact 

 that the results of my experiments indicate that differences in 

 tonal complexity are not utilized, later studies should show that 

 my tests did not offer complex enough klangs, they will be very 

 interesting in establishing a threshold for tonal sensitivity on 

 the basis of tonal complexity. 



Control 11. — This control was introduced to supplement con- 

 trols 6 and 7. In order to rule out the possibility that the data 

 there obtained were due to intrinsic differences in the whistles, 

 the one used in control 6 was placed over the apparatus in place 

 of the standard whistle and was sounded at the intensity of 

 control 7. Rat 47 was not tested, but the other two made 90% 

 and above. It may be concluded from this that for the rat 

 no intrinsic differences in the whistles were functionally effective. 



IV 



In instituting and continuing the series of tests with piston 

 whistles as just set forth, the writer was influenced by two 

 principle motives: (1) Uniform failure had waited upon all of 

 the work with tuning forks. It was hoped that with the whistle 

 positive data might be secured whose analysis would throw 

 light upon the problem of tone sensitivity. (2) It has been 

 suggested recently, notably by Yerkes, that where a difficult 

 discrimination is required of an animal, training should first 

 begin with a complex easily discriminable and gradually be 

 directed toward the aspect upon whose presence the problem 

 centers. When the present whistle tests had been begun pri- 



